LoongArch: Allow device trees be built into the kernel

During the upstream progress of those DT-based drivers, DT properties
are changed a lot so very different from those in existing bootloaders.
It is inevitably that some existing systems do not provide a standard,
canonical device tree to the kernel at boot time. So let's provide a
device tree table in the kernel, keyed by the dts filename, containing
the relevant DTBs.

We can use the built-in dts files as references. Each SoC has only one
built-in dts file which describes all possible device information of
that SoC, so the dts files are good examples during development.

And as a reference, our built-in dts file only enables the most basic
bootable combinations (so it is generic enough), acts as an alternative
in case the dts in the bootloader is unexpected.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 9 insertions, 3 deletions

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index d183a745fb85..15d366b8407c 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -295,8 +295,12 @@ static void __init fdt_setup(void)
 	if (acpi_os_get_root_pointer())
 		return;
 
-	/* Look for a device tree configuration table entry */
-	fdt_pointer = efi_fdt_pointer();
+	/* Prefer to use built-in dtb, checking its legality first. */
+	if (!fdt_check_header(__dtb_start))
+		fdt_pointer = __dtb_start;
+	else
+		fdt_pointer = efi_fdt_pointer(); /* Fallback to firmware dtb */
+
 	if (!fdt_pointer || fdt_check_header(fdt_pointer))
 		return;
 
@@ -330,7 +334,9 @@ static void __init bootcmdline_init(char **cmdline_p)
 		if (boot_command_line[0])
 			strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
 
-		strlcat(boot_command_line, init_command_line, COMMAND_LINE_SIZE);
+		if (!strstr(boot_command_line, init_command_line))
+			strlcat(boot_command_line, init_command_line, COMMAND_LINE_SIZE);
+
 		goto out;
 	}
 #endif